Vehicle drive trains known in practice typically comprise drive machines implemented as internal combustion engines, which in each case can be brought into operative connection with an output drive; where the drive machines each have a transmission apparatus having a plurality of shift elements that can be engaged or disengaged for implementing different transmission ratios in a power flow. The output drive is coupled to a transmission output shaft and the drive machine is coupled to a transmission input shaft of the transmission apparatus.
During progressions of operating states, during which an output speed is greater than zero and a driver of the vehicle removes his foot from the gas and the vehicle coasts, in conventional operating mode of the vehicle drive train, the vehicle brakes itself due to engine braking by the drive machine that is running connected.
Drivers who drive in a fuel-saving manner often find this braking undesirable. For this reason, a vehicle, in the presence of various operating state parameters, during a previously described operating state progression, transfers into a so-called sailing mode during which the drive machine is decoupled from the output drive, for example in the region of the transmission apparatus by interrupting the power flow between the transmission input shaft and the transmission output shaft, and switched off. Then, the vehicle continues rolling without burning fuel and without hindrance from a braking moment from the drive machine, whereby vehicle fuel consumption is reduced.
However, a problem here is that with the presence of a request for coupling to, or for producing the power flow in the transmission apparatus between the transmission input shaft and the transmission output shaft, an undesirably long period of time is necessary before the power flow is produced again the region of the transmission apparatus.